Contributors SMR, CRG and CNM conceived the idea for the study. CRG and SMR are guarantors. CRG, SMR, CNM, HMI, KMG, CML, CC and JL planned
the study, oversaw data collection and interpreted the results. CW carried out the cognitive and neuropsychological testing.
LDM and SMR derived the data on fatty acid intake in milk. CRG carried out the statistical analyses and wrote the first draft
of the manuscript. All authors subsequently revised the manuscript.

Accepted 27 October 2009

Published Online First 4 February 2010

Abstract

Objective To investigate the relation between breastfeeding, use of docosahexaenoic acid (DHA)-fortified formula and neuropsychological
function in children.

Design Prospective cohort study.

Setting Southampton, UK.

Subjects 241 children aged 4 years followed up from birth.

Main outcome measures IQ measured by the Wechsler Pre-School and Primary Scale of Intelligence (3rd edn), visual attention, visuomotor precision,
sentence repetition and verbal fluency measured by the NEPSY, and visual form-constancy measured by the Test of Visual-Perceptual
Skills (Non-Motor).

Results In unadjusted analyses, children for whom breast milk or DHA-fortified formula was the main method of feeding throughout
the first 6 months of life had higher mean full-scale and verbal IQ scores at age 4 years than those fed mainly unfortified
formula. After adjustment for potential confounding factors, particularly maternal IQ and educational attainment, the differences
in IQ between children in the breast milk and unfortified formula groups were severely attenuated, but children who were fed
DHA-fortified formula had full-scale and verbal IQ scores that were respectively 5.62 (0.98 to 10.2) and 7.02 (1.56 to 12.4)
points higher than children fed unfortified formula. However, estimated total intake of DHA in milk up to age 6 months was
not associated with subsequent IQ or with score on any other test.

Conclusions Differences in children's intelligence according to type of milk fed in infancy may be due more to confounding by maternal
or family characteristics than to the amount of long-chain polyunsaturated fatty acids they receive in milk.

Footnotes

Funding The Southampton Women's Survey is funded by the Medical Research Council and the Dunhill Medical Trust. The 4-year follow-up
of the children is funded by a research contract with the Food Standards Agency (contract no N05049). The study sponsors had
no role in the study design, in the collection, analysis or interpretation of data, in the writing of the report or in the
decision to submit the manuscript for publication.

Competing interests None.

Ethics approval Ethics approval was provided by the Southampton and South West Hampshire Local Research Ethics Committee.